The activated clay is the best decolourization reagent to the crude product, and 95% methanol is the best solvent for recrystallization. The 4 MDBT with 96.1% in purity and 61.6% in yield was obtained.

• 粗产品经活性白土脱色及在 - 2 0℃下用 95%25甲醇重结晶 2次后 ；产品纯度达 96 .；1%25；产率为6 1 6%25。